An apartment building under construction in the North Korean capital of Pyongyang has collapsed, causing an unspecified number of casualties, the state media reported Sunday.

The North's Korean Central News Agency said the accident occurred in the Pyongchon District on May 13 as "the construction of an apartment house was not done properly, and officials supervised and controlled it in an irresponsible manner."

An unidentified North Korean official apologizes to local citizens for the collapse of an apartment building under construction in Pyongyang. (Yonhap)

The KCNA reported that a "state emergency mechanism" was formed to rescue survivors and treat the wounded, and senior officials met with bereaved families and citizens in the district to express "deep consolation and (issue an) apology."

Among the ranking officials were Minister of People's Security Choe Pu-il, General Officer of the Korean People's Internal Security Forces Sonu Hyong-chol and Chairman of the Pyongyang City People's Committee Cha Hui-rim.

(Yonhap)

Leader "Kim Jong-un sat up all night, feeling painful after being told about the accident, instructed leading officials of the party, state and the army to rush to the scene, putting aside all other affairs, and command the rescue operation to recover from the damage as early as possible," the KCNA said in its English-version report, quoting a senior official.

It is rare for the state media to reveal facts about an accident that took place inside the reclusive country and for high-ranking officials to issue an official apology.

Although the media did not elaborate on the number of casualties, Seoul officials suspect a considerable number of people may have been killed in the collapse of the 23-story building.

"In North Korea, it is common that people move into a new apartment even before the construction is completed. About 92 households may have been living in the apartment," a South Korean government official said, asking for anonymity. (Yonhap)